Production of cylindrical ferrite rods by conventional manufacturing methods requires expensive and laborious centre-less diamond grinding to give a smooth walled cylinder that requires further diamond shaping still to taper the end sections of the rod. Each ferrite part must be individually ground and the dimensions and surface finish inspected prior to usage prior to inclusion into a device.
U.S. Pat. No. 6,673,181B1 discloses a fabrication process for ferrite toroids which utilizes ferrite ceramic tape having an improved elongation characteristic. The process utilizes a set of rigid mandrels which are employed in the final lamination to support the rectangular cross section of the internal cavity of a respective ferrite tube, thereby reducing stress concentration and permitting the highest lamination pressure to be used in the final step. The mandrels are removed prior to panel densification. The tape and mandrels operate together to minimize cracks and pores in the toroids and provide an added advantage of maintaining high tolerances in the internal cavity dimensions as well as the cavity-to-cavity alignment.
US 2003/169133 A1 discloses a transmission line comprising a first base having a substrate on which a groove is formed, a conductive film that is served as the ground electrode formed on the surface including said groove of said substrate, and dielectric material disposed on said conductive film of said groove portion. The transmission line comprises a second base having another conductive film that served as the ground electrode formed on the surface including said another substrate, and another dielectric material disposed on said another conductive film of said another groove portion, and a signal conductor, wherein said signal conductor is surrounded by dielectric material of said first base and dielectric material of said second base.